Increases max ammo capacity for shells, energy, bolts and explosives from 55 to 99.
Increases max ammo capacity for bullets from 255 to 555.

Ammo drops are dependent on the percent of ammunition held, so being out of ammo will lead to pickups being more frequent than if back muscle is not being run.

Any time an enemy is killed they have a 1 in 13(7.69%) chance of giving the player 1 HP applied automatically. While health drops are effected by current health, Bloodlust procs are not. This means that it can proc even if HP is full, to no additional benefit.

Regardless of max HP, if currently at 4 HP or below than any sort of explosive or fire damage will not deal damage to the player, thus making it impossible to die to these hazards.

Explosives usually hit twice in quick succession, but boiling veins prevents the additional hit during hurt animation.
In layman terms this means that explosions will only do half damage if taking the full blast of an explosive.

Any weapon that uses bolts will now behave differently, seeking enemies along their path

Normal bolts/splinters: If flying by an enemy, may quickly adjust direction to instead hit the enemy.
Large bolts: The same as normal bolts but homing is much weaker.
Seeker bolts: Increased homing radius and will take sharper turns to ensure hits.
Discs: Will bend towards nearby enemies, decreasing its speed which can cause extra hits.

Gives a multiplier of 0.3 to accuracy, where 0 is perfect accuracy. This will reduce the spread of weapon shots significantly.

Normal characters: Default accuracy 1, increased to 0.3.
Steroids: Accuracy 1.8, increased to 0.54.
Skeleton: Accuracy 1.5, increased to 0.45.

Any projectiles shot by enemies now go 20% slower. Does not effect enemy speed in any way.
Shields deflecting projectiles are not slowed, neither are some non-projectile attacks such as lasers.

Adds 0.5 to the total speed.
Floor hazards will no longer effect the player, which are cobwebs and ice flooring.

Mutants default speed is 4, bringing it to 4.5.
Plant's speed is 4.5, bringing it to 5.
Skeleton's speed is 3, bringing it to 3.5.
Big Dog's speed is 2, bringing it to 2.5.

The player now does contact damage to any enemies, at 6 damage a tick.
Enemies that deal contact damage will still hurt the player if not killed by gamma guts.
Standing still does 1 tick of damage at a time, meaning that contact damage enemies at 6 HP or below can safely be killed.
Meanwhile moving does 2 ticks of damage at a time, meaning that contact damage enemies at 12 HP or below can safely be killed.
It is recommended to constantly be moving while using this mutation on enemies.

Props are unaffected by gamma guts, as well as vans.

Enemies dying to gamma guts will cause a small shock around the player that does 8 additional damage to any enemies in the immediate vicinity.

Any wall can be walked into, destroying it.
20 wall tiles may be broken a level, the counter resets to 20 any time a new portal is entered.

A noticeable visual effect will appear when standing next to walls signifying that Hammerhead can be used.
Once all 20 tiles are used up, an audio cue will play to signify it can no longer be used that level.

Killing enemies will make their corpses fly substantially farther than their default distance.
Corpse damage is doubled, dealing 2 instead of 1.

Any weapon that uses energy ammo will deal additional damage. Each weapon laser type differs from each other, so 'additional damage' is rarely a flat percentage increase but rather higher damage potential.

Any weapon that is a melee, even if it uses ammo, gains "more range".
In actuality melee shots start further out from the player and are pushed forward at a higher velocity, covering more ground before it disappears.
This leaves a slight blind spot around the player, walking backwards from projectiles in imminent vicinity can avoid accidental hits.

Standing behind a wall will reduce melee range while running this mutation.
(Hugging a one wall tile will not effect Jackhammer as its projectile is simply moved forward with some slightly better range)

Any time an enemy is killed they have a 2 in 17(11.76%) chance of giving the player 1 ammo drops worth applied automatically.

The ammo type can be any of the 5 ammo types at random regardless of held weapons.

Every level will include an additional chest, which randomly chooses between a weapon chest, ammo chest and rad can.
Chest variations can also apply to these, such as becoming IDPD chests and present chests.
Exceptions to this is there cannot be two health chests in a level, two big weapon chests or two separately spawned hostile horrors.

Skipping 2 weapon chests in the same level counts as +50% towards spawning a big weapon chest.
Skipping 2 rad cans on the same level will spawn one hostile horror on the next.

Substantially increases the pickup range for drops.
Ammo & HP drops can be reached from much further away, as walking near the pickup suffices rather than walking almost directly over it.
Rads meanwhile are dragged in from the majority of the screen, meaning that just walking in the general direction of rads is enough to collect them.

Gives a flat +40% drop rate for ammo dropped by enemies.
As HP drops are converted from ammo, this in turn gives HP much more chances to drop dependent on health as well.

Any weapon that uses bullet ammo will give a 60% chance of returning that ammo to the player automatically, if the bullet makes contact with any prop or enemy.
Bullet weapons that use 1 ammo returns the 1, while bullet weapons that use 2 ammo will return 2 ammo instead.
Incinerator, Pop Gun & Pop Rifle are not effected by this mutation, instead being effected by Shotgun Shoulders. Every other weapon works as intended.

Increases the player's maximum HP by 4.
This automatically heals for the 4 new HP as well upon entering the next level.

Every enemy will have 20% of their max HP removed permanently.
This is always rounded to the nearest whole number.
Bosses and vans are included in this pool.
Any enemy that spawns midway through a level also has the reduced HP, such as IDPD.
Props are not effected by this.

Health drops give an additional 2 HP, for a total of +4 HP per drop.
This also effects health chests, which gives a total of +8 HP instead of the usual +4.

Any damage taken will be returned to all enemies on screen at 2.5x for damage taken.
This is not rounded; enemies will take the exact amount which can leave their health in the decimal points.
If taking more damage than health(losing spirit or going headless as Chicken), it will not deal additional damage; only the actual HP lost.
Similarly taking 0 damage at a time will not proc sharp teeth, such as boiling veins going into effect while at low HP.

Any weapon that uses shells will have the shells bounce back aggressively when in contact with a wall, traveling much further.
Shell weapons at point blank deals extra damage; this mutation also adds that damage to the moment shells bounce off walls, though just for two frames.

Flame weapons do not bounce normally; this lets them bounce once for a short distance.
Incinerator, Pop Gun & Pop Rifle are all effected by this mutation despite being bullet weapons.

Additional fire rate is given based on health lost.
The rate is percentage based, so the higher the max health the better the fire rate when low on HP.
Fire rate increase is Current HP / Max HP, for instance being at 50% health puts the players fire rate at 150%.

Any hit that would be lethal towards the player will instead be blocked by Strong Spirit, leaving the player at 1 HP instead. Until Spirit is regained any lethal hit will then kill the player.
In actual numbers, a lethal hit consuming Spirit will give about 5 frames of invulnerability. Where there are some damage sources that ignore iframes, this can prevent those from an insta-kill.

In order to regain Strong Spirit, the level Spirit was lost on must be completed. Upon reaching full HP at any following level, Spirit will be recharged and will be there to protect the player once again.
If max HP is at 1 (Chicken/Melting) than Strong Spirit can only ever be used once. It will never recharge unless if max HP is 2 or above.

Thronebutt will enhance each characters specific active ability. In-depth tech on these can be found on their respective character tech pages. A shortened version is as follows:

• Fish: "Water Boost"
• Gives infinite roll with more control.
• Crystal: "Teleportation; Shorter Shielding"
• Eyes: "Stronger Telekinesis"
• Melting: "Bigger Corpse Explosions"
• Plant: "Snare Finishes Enemies Under 33% HP"
• YV: "BRRRAP"
• Pop Pop effect is doubled.
• Steroids: "Firing Gives Ammo For Your Other Weapon; More Effective When Firing Both"
• Robot: "Better Weapon Nutrition"
• Eating ammo gives an additional drop.
• Chicken: "Throws Pierce Through Enemies"
• Rebel: "Higher Ally Rate Of Fire"
• Horror: "Beam Charges Up Faster; Prolonged Beam Use Heals You"
• Rogue: "Stronger Portal Strike"
• Skeleton: "Better Odds"
• Blood Gamble is less likely to injure Skeleton.
• Frog: "Toxic Gas Spreads Faster"
• Big Dog: "Faster Missile And Bullets"

Any time an enemy is killed 40% of the remaining reload time is removed from both held weapons.

Skips the current set, giving a new set instead after entering the next exit portal.
Once Patience is taken, will not reappear.

What the new set gives is dependent on version and has more complicated mechanics behind the scene.
Deeper reading can be done here(Link Later), but in a normal run it can just be viewed as a random reroll.

Last Wish will cure the player, healing them back to max HP.
Gives 20 shells, energy, bolts and explosive ammo, while 200 ammo for bullets.
Held weapons will have the curse debuff removed if applicable.

Additionally functions as a much slower patience, if taken a special flower will spawn on 5-1.
If the flower is fed 4 HP, it will take the player to the secret Jungle area.
Last Wish will be consumed, and a new mutation set will appear.
Last Wish will be re-added to the mutation pool, as rerolls can be done again in loop.

Heavy Heart is a secret mutation that will only appear if 3 of the 6 weapon-specific mutations are taken in a run.
These include: Boiling Veins, Bolt Marrow, Laser Brain, Long Arms, Recycle Gland, and Shotgun Shoulders.
Guaranteed to be the first mutation slot of the next set seen after the condition is met.

Increases enemies chances of dropping weapons by 210%, more than double.
As it's multiplicative only enemies that already drop weapons(Link Later) are effected, unlike Crown of Guns which adds a flat rate.
(However Heavy Heart & Crown of Guns can be stacked to that effect.)

Fish's Ultra A mutation that has a 20% chance to convert any enemy drop into a chest instead. Ammo drops become ammo chests, weapon drops become weapon chests and health drops become health chests.

Fish's Ultra B mutation that makes ammo not be consumed for the first 7 seconds any time a new stage is entered, weapon cooldowns still apply.

Crystal's Ultra A mutation that gives her an additional 6 max HP. Can be stacked with Rhino Skin.

Crystal's Ultra B mutation that allows her to move during her shield time.

Eyes' Ultra A mutation that brings any active projectiles he shot back to him by using telekensis, and can be held in place around him or fired out another time.

Eyes' Ultra B mutation that pushes enemies away from him for a radius that covers most of the screen.

Melting's Ultra A mutation that lets him use his active on alive enemies if they're under 5 HP.

Melting's Ultra B mutation that gives him an additional 3 mutation pools to choose from at the cost of half of his current max HP. Adding extra HP afterwards(Rhino Skin) will not be halved.

Plant's Ultra A mutation that adds 5 snares around the main snare for a total of 6.

Plant's Ultra B mutation that will spawn sapling allies from enemies killed on snares whose blood explosions upon death can erase projectiles and damage enemies, and can do contact damage themselves.

YV's Ultra A mutation that gives him an additional +40% firerate.

YV's Ultra B mutation that gives an extra pop to his active without costing extra ammo or reload time.

Steroids' Ultra A mutation makes weapon chests always drop the same weapon twice, which also means twice the ammo for that weapon type.

Steroids' Ultra B mutation makes ammo & present chests now give ammo for all 5 ammo types when opened.

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Chicken's Ultra A mutation lets her kill enemies to increase the timer on her headless state for 1 more second each, though it can never surpass 5 seconds.

Chicken's Ultra B mutation that makes weapons return to her secondary weapon slot once the weapon comes to a stop.

Rebel's Ultra A mutation that automatically gives her two allies for free at the start of a new stage, and all allies health will be at 30 HP instead of 12 HP.

Rebel's Ultra B mutation that lets her always summon 2 allies at a time instead of 1, always at the cost of 2 HP.

Horror's Ultra A mutation that makes destroyed enemies/props that drop radiation upon death will also burst into radiation pellets that cause 1 damage to enemies each.

Horror's Ultra B mutation that will automatically kill every enemy in the level if their combined health totals less than 140 HP.

Horror's Ultra C mutation that increases the ultra rad meter from 600 rads to 1,200 rads, allowing for more rad beam or ultra weapon usage.

Rogue's Ultra A mutation that lets her have up to 6 portal strikes and canisters will give 2 portal strikes instead; 1 is still consumed per. shot.

Rogue's Ultra B mutation that when damaged triggers 6 blast explosions around her instead of the usual 3 giving much more coverage/range.

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The Ultra A co-op ultra, any health pickup/chest now will apply to both characters.

The Ultra B co-op ultra, any ammo pickup/chest now will apply to both characters.
Whoever picks up ammo will have the drop chances apply to them, and then that ammo type will also be shared with the player.
However opening an ammo chest will give ammo both specific to each players' primary weapon independent of each other.